I have a g550 dual head vga/dvi card and Ubuntu Hardy Heron. The driver I'm using is the one from the Ubuntu CD installation disk. Everything is working fine and I have the screen resolution at 1280x960 (maximum I can set it, even though I know that my monitor is capable of 1280x1024 and the card even higher resolutions) but every time I enable the desktop effect, everything goes really really SLOW.

Do you think, that if I try installing "matroxdriver_mga-x86_32-4.4.4-installer.run",this will fix my problem?

What driver is currently installed on your system? The Xorg mga driver or one of the official/unofficial mga driver versions from Matrox/me?The Xorg mga driver itself does _NOT_ support hardware acceleration at a satisfiable level, so if you're looking for hardware acceleratoin, 4.4.4 is the way to go for you.

It may also be able to fix your resolution problem because the unofficial mga driver features a different way to set Modelines, so yes, if you're currently running the Xorg mga driver, the unofficial driver will help you.